The invention relates generally to the measurement of water current, and more particularly to a method and system that provides for the non-invasive measurement of water current magnitude and direction.
A variety of small unmanned underwater vehicles are in development and use today. In situations where precision navigation is critical (e.g., mine clearing activities carried out by torpedo-like vehicles), surface and/or underwater currents can affect navigation performance and, therefore, affect the outcome of a vehicle""s mission. Accordingly, it would be beneficial to know what the surface and/or bulk underwater currents are prior to vehicle deployment in order to aid in selection of vehicle heading, speed, operating depth, etc. Ideally, measurement of surface and/or bulk underwater currents would be accomplished non-invasively (i.e., no measurement device need be placed in the water) from a remote location.
Accordingly, it is an object of the present invention to provide a method and system for measuring water currents in a body of water.
Another object of the present invention is to provide a non-invasive method and system for measuring water currents.
Still another object of the present invention is to provide a method and system for measuring surface and/or bulk underwater currents.
Yet another object of the present invention is to provide a method and system for remotely measuring surface and/or bulk underwater currents.
Other objects and advantages of the present invention will become more obvious hereinafter in the specification and drawings.
In accordance with the present invention, a method and system are provided for measuring water current direction and magnitude. A plurality of beams of radiation are transmitted radially outward from a location above a body of water. Each beam is incident on the water""s surface at an angle with respect thereto. Each beam experiences a Doppler shift as a result of being incident on the water""s surface such that a plurality of Doppler shifts are generated. Each Doppler shift is measured with the largest one thereof being indicative of water current direction and magnitude. For bulk underwater current measurements, the transmitted beams have a wavelength in the blue-green spectral region. For surface current, the transmitted beams have a wavelength outside the blue-green spectral region. If both surface and bulk underwater currents are to be measured, the transmitted beams can be multiple wavelength beams having wavelength components both within and outside of the blue-green spectral region.